Marking pen



FIG. 1 is a perspective view of a marking pen showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof;

FIG. 8 is an enlarged left side view thereof; and,

FIG. 9 is an enlarged right side view thereof. 

CLAIM The ornamental design for a marking pen, as shown and described. 